Method and apparatus for the production of iron or steel

ABSTRACT

An iron or steelmaking process in which particles of coke or iron ore are fed into a horizontally-disposed furnace which rotates at high speed. The particles enter a discharge tube by means of a slot in the tube wall and are ejected from the discharge end of the tube into the furnace by pulses of compressed air, thus spreading the particles over the length of the furnace.

United States Patent 1 [111 3,740,044 Uemlianin June 19, 1973 METHOD AND APPARATUS FOR THE PRODUCTION OF IRON OR STEEL Primary ExaminerGerald A. Dost [75] Inventor: Andray Uemlianin, Redcar, England Attorneymleo Rosetta [73] Assignee: The British Iron and Steel Research Association, London, England [57] ABSTRACT [22] Filed: Jan. 19, 1972 [2]] Appl 3 3 An iron or steelmaking process in which particles of coke or iron ore are fed into a horizontally-disposed furnace which rotates at high speed. The particles enter [52] US. Cl. 266/36 H, 75/33 a discharge tube by means ofa Slot in the tube wall and [51] hit. Cl. C216 5/28 are ejected from the discharge and of the b into the [58] Field Of Search 75/33, 36; 266/36 H furnace by pulses of compressed air thus Spreading the particles over the length of the furnace. [56] References Cited UNITED STATES PATENTS 10 Claims, 7 Drawing Figures 3,663,201 5/1972 Heitmann 75/36 37 5 7 7 x 3 2 5 3 I 6 I I I I I I PAIENIE JUN 1 9 ms sum 1 ur 4 PAIENIEDJUNIQIQTS v 3,740,044

SHEEI 2 [IF 4 PAIENIE JUN 1 9 ma sum 3 0f 4 PAIEMEU JUN1 9 ma SHEET t 01- 4 mm QX METHOD AND APPARATUS FOR THE PRODUCTION OF IRON OR STEEL In processes for the continuous production of iron or steel, there is a requirement for the processing vessel to be fed continuously or semi-continuously with raw materials. In conventional batch processes, such as the well known L.D. process for the production of steel,

the raw material is fed into the processing vessel primarily at the commencement of each batch.

In a generally horizontally-disposed rotary furnace certain problems arise in the distribution of raw material to the furnace. It has been found that the feeding of raw material into one end of the furnace and allowing the material to gradually spread along the furnace wall gives rise to severe refractory wear in the area close to the feed end of the furnace. Additionally, an accumulation of unmelted material at the feed end of the furnace prevents the flow of material along the length of the furnace and lowers the rate of reaction due to a lowering of the temperature in the area of the accumulation.

According to one aspect of the invention, a process is provided for the production of iron or steel including rotating a refractory-lined, generally horizontallydisposed rotary furnace about its axis at such a speed that the liquid and solid furnace contents are maintained around the internal wall of the furnace by centrifugal force, the said contents comprising liquid metal forming an outer layer in contact with the refractory lining and a non-metallic material forming an inner layer, and introducing particulate material required for the production of iron or steel into the furnace with an alternately decreasing and increasing horizontal component of motion so as to spread the material along the length of the furnace.

According to another aspect of the invention an iron or steelmaking apparatus is provided including a refractory-lined, generally horizontally-disposed rotary furnace and means for introducing particulate material into the furnace with an alternately decreasing and increasing horizontal component of motion.

By the term generally horizontally-disposed we mean that the longitudinal axis of the furnace may be inclined at up to eight degrees from the horizontal.

We have found that the invention gives rise tosubstantial improvements in the life of the furnace lining. The best results are obtained if the particulate material is entrained in a compressed fluid prior to its introduction into the furnace. The compressed fluid is preferably pulsed at regular intervals, these intervals being controlled by a suitable actuator and timing device. The duration of the pulse may be greater than the interval of time between the pulses, and the fluid may suitably be a gas such as air.

The particulate material is preferably introduced into the furnace by means including a discharge tube, one end of which is adapted to be connected with a supply of compressed fluid, there being an opening in the tube wall by which particulate material enters the tube, and means for passing the compressed fluid from one end of the tube along the tube to eject particulate material from the discharge end of the tube.

Preferably a housing surrounds that part of the tube having the opening in the tube wall, and at least part of the tube is rotatable about its longitudinal axis relative to the housing. The tube may be in several parts connected with one another and one or more of these parts may be rotatable about their longitudinal axes.

The size of the opening in the tube wall may be adjustable. The opening is preferably in the form of a slot. The length of the slot may be adjustable and/or the width may be adjustable. The tube within the housing may be in two parts, one part being concentric with and within the other part and each part having an opening in the form of a slot, the parts being moveable relative to one another in an axial direction so that the composite slot formed by the coincidence of the slots in each of the respective parts is adjustable in length. The two parts of the tube may be rotatable relative to one another, so that the composite slot formed by the coincidence of the slots in each of the respective parts is adjustable in width. By this means different quantities of particulate material can enter the tube before being ejected, for different settings of the adjustments.

The invention thus provides a solution to the problem of severe local refractory wear and also gives a significant rise in the output of the furnace.

In the accompany drawings FIG. I shows a longitudinal section through one embodiment of an apparatus for carrying out the process according to the invention;

FIG. 2 shows a schematic diagram of an embodiment of the apparatus according to the invention;

FIGS. 3 and 4 show details of the apparatus,

FIG. 5 shows a cut-away section on the line V V of FIG. 3;

FIG. 6 shows a modification of the detail of FIG. 3, and i FIG. 7 shows a section of line VII VII of FIG. 6.

A rotary furnace l for the production of iron or steel is shown in FIG. 1. The furnace consists of a cylindrical furnace shell 2 with a refractory lining 3. Two annular rails 5 surround the shell 2 adjacent each end of the shell 2 and are engaged by rollers (not shown) mounted on frame 4. The furnace 1 is generally horizontallydisposed, its longitudinal axis inclined at approximately 3 to the horizontal.

The furnace can be rotated about its longitudinal axis by a drive motor (notshown) at such a speed that the liquid and solid furnace contents are maintained around the internal wall of the fumace by centrifugal force.

Externally of the furnace l is a housing 14 which includes a discharge tube 6 for introducing particulate material into the furnace. This housing 14 is more fully described later with reference to FIGS. 2 to 5.

Particulate material required for the production of iron or steel is introduced into the furnace 1 through tube 6. Additional material may be introduced into the furnace l by tube 7. The particulate material includes one or more of the following: iron ore, iron pellets, sinter, pre-reduced agglomerate, coal, coke, limestone.

A burner 8 is provided at the upper or inlet end of furnace l, and is directed so as to produce a flame along the length of the furnace.

The furnace l is open at each end, and the upper or inlet end is surrounded by a refractory lined hood 31 through which tubes 6 and 7 and hunter 8 project. The outlet end of the furnace is alsosurrounded by a refractory lined hood 32 which has an outlet 33 for waste gas. The bottom of the hood 32 has tapping holes 10 and l l.

In FIG. 2 the apparatus for supplying particulate material to the furnace 1 is shown in schematic form.

A hopper 12 is connected by a flexible hose 13 to a housing 14. The tube 6 passes through housing 14 and is connected with a ball valve'15 operated by an actuator 16. A timer 17 controls the actuator 16. A compressed air supply 18 is connected to the end of tube 6 remote from the discharge end 1 by means of a flexible pipe 19, a flow-meter 20, an on/off valve 22, a flow control valve 21 and a pressure regulator valve 23. A pressure gauge 34 is connected between the flow control valve 21 and the on/off valve 22.

Details of the housing 14 and associated apparatus are shown more clearly in FIGS. 3, 4, and 5. The tube 6 is in two parts connected by coupling 24 which is attached rigidly to the housing 14. The part of tube 6 on the side of coupling 24 distant from the furnace l is rotatable about its own axis relative to the housing 14. An arm 25 connected with a pointer 26 is rigidly attached to tube 6 so that tube 6 can be rotated by an amount indicated by the pointer 26 on a scale 27 which is rigidly attached to housing 14.

An opening 28 in the form of a slot is provided in the wall of the part of tube 6 which is within the housing 14. The slot is substantially rectangular in plan view as seen in FIG. 4, but one longer side 30 of the slot extending in the direction of the axis of tube 6 is bowed slightly so as to increase the area of the slot.

An inspection and cleaning entry 29 forms part of the housing 14 although this entry is normally blanked off.

A modification of the apparatus is shown in FIGS. 6 and 7 and comprises a tube 6 in two parts 40 and 41 one part 41 being concentric with and within the other part 40. Both parts 40 and 41 have an opening 42 and 43 respectively in the form of a slot in their walls. Parts 40 and 41 are adjustable relative to one another in an axial direction so that the composite slot 44 formed by the coincidence or partial coincidence of slots 42 and 43 in each of the respective parts 40 and 41 is adjustable in length. Parts 40 and 41 are also rotatable relative to one another so that the composite slot 42 is adjustable in width. The modification of tube 6 permits adjustment for different feed rates of material.

In the production of iron, particulate material in the form of iron ore, coal and limestone is supplied to the hopper 12 by a screw conveyor (not shown) or other suitable known conveyors. The material will fall by gravity into the flexible hose 13 and thus into the housing 14. At the same time, compressed air is supplied to the end of tube 6 at a pressure and flowrate adjusted by means of the valve 21, regulator valve 23 and flowmeter 20. The timer 17 is set so that the actuator 16 opens and closes the ball valve 15 at predetermined intervals, so that compressed air passes along tube 6 for predetermined periods of time.

Some of the particulate material entering the housing 14 by means of the flexible hose 13 will also enter the tube 6 by way of the opening 28. The amount of material which enters the tube 6 in a given time is partly dictated by the area which the opening 28 presents to the material as it enters the housing 14. Thus the quantity of particulate material entering the furnace l per unit time can be controlled by rotating the tube 6 so that the opening 28 presents a suitable area to the material entering the housing 14. When it is desired to change the quantity of particulate material entering the furnace l per unit time, the tube 6 is rotated by arm 25 to a position where the opening 28 presents a greater or a smaller area to the material entering the housing 14. It has been found that a bowed side 30 to the opening 28 facilitates the flow of material into the tube 6 at positions where the area presented by the opening 28 is small.

A calibration curve can be drawn up for a given material and a given ball valve opening and closing time sequence showing the change in the quantity of material passing through the tube 6 per unit time as a function of the position of the opening 28 as indicated by the pointer 26 and scale 27.

The material entering tube 6 by opening 28 is entrained in the compressed air and ejected at intervals from the end of the tube directed into furnace 1 by pulses of compressed air passing down the tube 6 at regular intervals.

The ball valve 15 is controlled so that it opens rapidly and closes slowly, thus causing the particulate material to enter the furnace l with an alternately decreasing and increasing horizontal component of motion. Part of the material is distributed to the end of the furnace 1 distant from tube 6, whilst part is distributed nearer the end of the furnace 1 close to tube 6, thus spreading the material along the length of the furnace. The speed at which the ball valve 15 closes can be altered in order to change the spreading characteristics of the material. Alternatively the spreading characteristics can be changed by altering the airflow and/or air pressure. The trajectory of the material can be changed by altering the air pressure by means of the pressure regulator valve 23.

In this way it is possible to control both the quantity of material entering the furnace per unit time and distribution of material over the length of the furnace. The problems of severe refractory wear in one part of the furnace lining can thereby be reduced.

The particulate material for the production of iron, i.e., iron ore, coal and limestone, which is spread along the length of the furnace, reacts in the following way. The carbon in the coal reduces the ore to iron and carbon monoxide, and oxygen present in the flame oxides the resultant carbon monoxide to carbon dioxide thus releasing heat required to maintain the reduction process. Under the centrifugal force due to the rotation of the furnace, the various liquid and solid constituents of the furnace contents segregate into separate layers, the heaviest constituent, iron, being maintained as the outer layer against the refractory surface. The inner layer consists of non-metallics or slag produced by the reactions of the limestone with the impurities in the iron.

The process can be run as a continuous process and as materials are continuously introduced into the furnace from the inlet end, liquid iron and slag pours into the collecting hood 32 at the outlet and is collected through tapping holes 10 and 11 respectively.

The process may be used to produce either iron or steel according to the type of atmosphere present within the furnace. The type of atmosphere (e.g., oxidising, reducing or partially reducing) can be controlled by bumer design and operating conditions ineluding fuel/oxygen ratios and fine coal additions.

We claim:

1. A process for the production of iron or steel wherein, a refractory-lined, generally horizontallydisposed rotary furnace is rotated about its axis at such a speed that the liquid and solid furnace contents are maintained around the internal wall of the furnace by centrifugal force, the said contents comprising liquid metal forming an outer layer in contact with the refractory lining and a non-metallic material forming an inner layer lying on the metal layer, and wherein particulate material required for the production or iron or steel is introduced into the furnace with an alternately decreasing and increasing horizontal component of motion so as to spread the material along the length of the furnace.

2. A process according to claim 1, wherein the particulate material is introduced into the furnace through a discharge tube, one end of which is adapted to be connected with a supply of compressed fluid, there being an opening in the tube wall by which particulate mate rial enters the tube, and the compressed fluid is passed from one end of the tube along the tube to eject particulate material from the discharge end of the tube.

3. A process according to claim 2 wherein the compressed fluid is pulsed at regular intervals.

4. A process according to claim 3 wherein the pulse duration is greater than the interval between the pulses.

5. Iron-making or steel-making apparatus comprising a refractory-lined, generally horizontally-disposed rotary furnace and means for introducing particulate material into the furnace with an alternately decreasing and increasing horizontal component of motion so as to spread the material along the furnace.

6. Apparatus according to claim 5 including a discharge tube, one end of which is adapted to be connected with a supply of compressed fluid, there being an opening in the tube wall by which particulate material enters the tube, and means for passing the compressed fluid from one end of the tube along the tube to eject particulate material from the discharge end of the tube.

7. Apparatus according to claim 6 including means for pulsing the compressed fluid.

8. Apparatus according to claim 7 wherein the size of the opening in the tube wall is adjustable.

9. Apparatus according to claim 8 wherein the tube is in two parts, one part being concentric with and within the other part and each part having an opening in the form of a slot, the parts being movable relative to one another in an axial direction so that the composite slot formed by the coincidence of the slots in each of the respective parts is adjustable in length.

10. Apparatus according to claim 9 wherein the two parts of the tube are adapted to be rotatable relative to one another, so that the composite slot formed by the coincidence of the slots in each of the respective parts is adjustable in width. 

2. A process according to claim 1, wherein the particulate material is introduced into the furnace through a discharge tube, one end of which is adapted to be connected with a supply of compressed fluid, there being an opening in the tube wall by which particulate material enters the tube, and the compressed fluid is passed from one end of the tube along the tube to eject particulate material from the discharge end of the tube.
 3. A process according to claim 2 wherein the compressed fluid is pulsed at regular intervals.
 4. A process according to claim 3 wherein the pulse duration is greater than the interval between the pulses.
 5. Iron-making or steel-making apparatus comprising a refractory-lined, generally horizontally-disposed rotary furnace and means for introducing particulate material into the furnace with an alternately decreasing and increasing horizontal component of motion so as to spread the material along the furnace.
 6. Apparatus according to claim 5 including a discharge tube, one end of which is adapted to be connected with a supply of compressed fluid, there being an opening in the tube wall by which particulate material enters the tube, and means for passing the compressed fluid from one end of the tube along the tube to eject particulate material from the discharge end of the tube.
 7. Apparatus according to claim 6 including means for pulsing the compressed fluid.
 8. Apparatus according to claim 7 wherein the size of the opening in the tube wall is adjustable.
 9. Apparatus according to claim 8 wherein the tube is in two parts, one part being concentric with and within the other part and each part having an opening in the form of a slot, the parts being movable relative to one another in an axial direction so that the composite slot formed by the coincidence of the slots in each of the respective parts is adjustable in length.
 10. Apparatus according to claim 9 wherein the two parts of the tube are adapted to be rotatable relative to one another, so that the composite slot formed by the coincidence of the slots in each of the respective parts is adjustable in width. 